JP5170529B2 - Fuel cell system and control method thereof - Google Patents

Description

  The present invention relates to a fuel cell system and a control method thereof.

  2. Description of the Related Art Conventionally, a fuel cell system including a fuel cell that generates power by receiving a supply of reaction gas (fuel gas and oxidizing gas) has been proposed and put into practical use. Such a fuel cell system is provided with a supply channel for flowing fuel gas supplied from a fuel supply source such as a hydrogen tank to the fuel cell. Currently, an electromagnetically driven on-off valve such as an injector is disposed in the supply channel of the fuel cell system, and the supply pressure of the fuel gas in the supply channel is adjusted by controlling the operating state of the on-off valve. Has been proposed.

Incidentally, in recent years, a circulation channel for circulating and reusing the fuel gas contained in the gas discharged from the fuel cell to the supply channel, and forcing the gas in the circulation channel to the supply channel A fuel circulation type fuel cell system provided with a circulating pump is proposed (for example, see Patent Document 1). In such a fuel circulation type fuel cell system, the supply flow path and the circulation flow path are for the purpose of suppressing the influence of the combined pressure of the gas flowing in the supply flow path and the gas flowing in the circulation flow path. Is often arranged downstream of the on-off valve.
JP 2007-35450 A

  However, in the conventional fuel circulation type fuel cell system as described above, moisture existing at the junction of the supply flow path and the circulation flow path in the low temperature environment (for example, below freezing point) is upstream (opening / closing valve side). There was a possibility that the water flowed back and the flowed water was frozen in the downstream portion of the on-off valve, and the supply flow path was blocked.

  The present invention has been made in view of such circumstances, and an on-off valve that adjusts the supply pressure of the fuel gas in the supply flow path, and a circulation pump that forcibly sends the gas in the circulation flow path to the supply flow path And a fuel cell system comprising: a supply channel in a low temperature environment.

  In order to achieve the above object, a fuel cell system according to the present invention includes a fuel cell, a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, and a gas upstream of the supply channel. An on-off valve that adjusts the state and supplies it to the downstream side, a circulation channel that guides the gas discharged from the fuel cell to the supply channel, and a gas that is exhausted from the fuel cell is forcibly sent to the supply channel A fuel cell system comprising a circulation pump, wherein a joining portion between the supply passage and the circulation passage is disposed downstream of the on-off valve, and the fuel to the joining portion by the on-off valve in a low temperature environment Control means for synchronizing the gas injection timing and the gas discharge timing to the junction by the circulation pump is provided.

  In addition, the control method according to the present invention includes a fuel cell, a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, and a gas state on the upstream side of the supply channel by adjusting the gas state downstream. An on-off valve that supplies gas to the side, a circulation channel that guides the gas discharged from the fuel cell to the supply channel, and a circulation pump that forcibly sends the gas discharged from the fuel cell to the supply channel The control method of the fuel cell system in which the joining portion between the supply passage and the circulation passage is arranged downstream of the on-off valve, and injecting fuel gas to the joining portion by the on-off valve in a low temperature environment A step of synchronizing the timing with the timing of gas discharge to the junction by the circulation pump.

  By adopting such a configuration and method, in a low temperature environment, it is possible to synchronize the fuel gas injection timing to the junction with the on-off valve and the gas discharge timing to the junction with the circulation pump. In this case, it is possible to suppress the water present in the junction between the supply channel and the circulation channel from flowing back to the upstream side (opening / closing valve side) and freezing in the downstream portion of the opening / closing valve. Accordingly, the power generation state of the fuel cell can be stabilized by suppressing the blockage of the supply channel in a low temperature environment. Here, “under a low temperature environment” means an environment in which moisture present in the supply flow path or the junction is frozen (for example, in an environment where the temperature in the downstream portion of the on-off valve of the supply flow path is below the freezing point). Means.

  In the fuel cell system, an injector can be employed as the on-off valve. An injector is an electromagnetically driven opening and closing that can adjust the gas state (gas flow rate and gas pressure) by driving the valve body directly with a predetermined driving cycle with electromagnetic driving force and separating it from the valve seat It is a valve. The predetermined control unit drives the valve body of the injector to control the fuel gas injection timing and injection time, whereby the flow rate and pressure of the fuel gas can be accurately controlled.

  According to the present invention, in a fuel cell system comprising: an on-off valve that adjusts the supply pressure of the fuel gas in the supply flow path; and a circulation pump that forcibly sends the gas in the circulation flow path to the supply flow path. It is possible to suppress blockage of the supply flow path in a low temperature environment.

  Hereinafter, a fuel cell system 1 according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, an example in which the present invention is applied to an on-vehicle power generation system of a fuel cell vehicle will be described.

  First, the configuration of the fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, the fuel cell system 1 according to the present embodiment includes a fuel cell 2 that generates power by receiving supply of reaction gas (oxidation gas and fuel gas). Gas to the fuel cell 2 and the oxidizing gas system 3 for discharging the oxidizing off gas from the fuel cell 2, hydrogen gas as the fuel gas to the fuel cell 2 and hydrogen off gas as the fuel off gas to hydrogen gas In addition, a fuel gas system 4 to be circulated to the fuel cell 2 is connected. The fuel gas system 4 has an exhaust drain valve 29 that can discharge hydrogen off gas from the fuel gas system 4, and the hydrogen off gas discharged from the exhaust drain valve 29 is discharged from the oxidizing gas system 3 in the dilution section 5. It can be discharged to the outside after being mixed with (air). The entire system is centrally controlled by the control unit 6.

  The fuel cell 2 is formed of, for example, a solid polymer electrolyte type and has a stack structure in which a large number of single cells are stacked. The unit cell of the fuel cell 2 has an air electrode (cathode) on one surface of the solid polymer electrolyte membrane, a fuel electrode (anode) on the other surface, and further sandwiches the air electrode and the fuel electrode from both sides. It has a pair of separators so as to be depressed. The fuel cell 2 generates electric power by supplying the fuel gas to the flow path of the separator on the anode side and the oxidizing gas to the flow path of the separator on the cathode side.

  Since the electrochemical reaction in the fuel cell 2 is an exothermic reaction, heat is supplied into the fuel cell system 1 according to the output during operation of the fuel cell 2. Therefore, even in a low temperature environment, while the fuel cell 2 is in operation, the temperature of the components in the system is increased by supplying the off-gas and the like heated in the fuel cell 2 to each piping system. Therefore, freezing is normally avoided during operation of the fuel cell 2. The fuel cell system 1 is provided with a refrigerant piping system (not shown). And by circulating a refrigerant | coolant inside the fuel cell 2 using this refrigerant | coolant piping system, the temperature inside the fuel cell 2 is maintained moderately.

  The oxidizing gas system 3 has an air supply passage 11 through which oxidizing gas supplied to the fuel cell 2 flows, and an exhaust passage 12 through which oxidizing off-gas discharged from the fuel cell 2 flows. The air supply flow path 11 includes an air compressor 14 that takes in air as an oxidizing gas, and a humidifier 15 that humidifies the air pressure-fed by the air compressor 14. The exhaust passage 12 includes a back pressure adjustment valve 16 and is connected to the humidifier 15, and the oxidizing off gas flowing through the exhaust passage 12 passes through the back pressure adjustment valve 16 and is used for moisture exchange in the humidifier 15. After that, it is transferred to the dilution unit 5.

  The fuel gas system 4 includes a hydrogen tank 21 as a fuel supply source storing high-pressure hydrogen gas, a hydrogen supply passage 22 for supplying the hydrogen gas in the hydrogen tank 21 to the fuel cell 2, and an exhaust from the fuel cell 2. And a circulation flow path 23 for returning the hydrogen off gas thus returned to the hydrogen supply flow path 22. Instead of the hydrogen tank 21, a reformer that generates hydrogen-rich reformed gas from a hydrocarbon-based fuel, a high-pressure gas tank that stores the reformed gas generated by the reformer in a high-pressure state, and Can also be employed as a fuel supply source. A tank having a hydrogen storage alloy may be employed as a fuel supply source.

  The hydrogen supply flow path 22 is provided with a shut-off valve 24 that allows or blocks the supply of hydrogen gas from the hydrogen tank 21, a regulator 25 that adjusts the pressure of the hydrogen gas, and an injector 26. Further, a temperature sensor 27 for detecting the temperature in the hydrogen supply flow path 22 is provided on the downstream side of the injector 26 and upstream of the junction A between the hydrogen supply flow path 22 and the circulation flow path 23. . Information relating to the temperature in the hydrogen supply flow path 22 on the downstream side of the injector 26 detected by the temperature sensor 27 is transmitted to the control unit 6 and used for control of the hydrogen circulation system.

  The regulator 25 is a device that regulates the upstream pressure (primary pressure) to a preset secondary pressure. In the present embodiment, a mechanical pressure reducing valve that reduces the primary pressure is employed as the regulator 25. The mechanical pressure reducing valve has a structure in which a back pressure chamber and a pressure adjusting chamber are formed with a diaphragm therebetween, and the primary pressure is reduced to a predetermined pressure in the pressure adjusting chamber by the back pressure in the back pressure chamber. Thus, a publicly known configuration for the secondary pressure can be employed.

  The injector 26 is an electromagnetically driven on-off valve capable of adjusting the gas flow rate and the gas pressure by driving the valve body directly with a predetermined driving cycle with an electromagnetic driving force and separating it from the valve seat. In the present embodiment, as shown in FIG. 1, an injector 26 is disposed on the upstream side of the junction A between the hydrogen supply channel 22 and the circulation channel 23. The injector 26 includes a valve seat having an injection hole for injecting gaseous fuel such as hydrogen gas, a nozzle body for supplying and guiding the gaseous fuel to the injection hole, and an axial direction (gas flow direction) with respect to the nozzle body. And a valve body that is slidably accommodated and opens and closes the injection hole. In the present embodiment, the valve body of the injector 26 is driven by a solenoid that is an electromagnetic drive device, and the opening area of the injection hole is made two or more stages by turning on and off the pulsed excitation current supplied to the solenoid. It can be switched. By controlling the gas injection time and gas injection timing of the injector 26 by the control signal output from the control unit 6, the flow rate and pressure of the hydrogen gas are controlled with high accuracy. The injector 26 directly opens and closes the valve (the valve seat and the valve body) with an electromagnetic driving force, and has a high responsiveness because its driving cycle can be controlled to a highly responsive region.

  The injector 26 changes the opening area (opening) and / or the opening time of a valve provided in the gas flow path of the injector 26 in order to supply the required gas flow rate downstream thereof. The gas flow rate (or hydrogen molar concentration) supplied to the (fuel cell 2 side) is adjusted. Since the gas flow rate is adjusted by opening and closing the valve of the injector 26 and the gas pressure supplied downstream of the injector 26 is reduced from the gas pressure upstream of the injector 26, the injector 26 is regulated by a pressure regulating valve (pressure reducing valve, regulator). Can also be interpreted. The injector 26 also functions as a variable pressure control valve capable of changing the pressure adjustment amount (pressure reduction amount) of the upstream gas pressure so as to match the required pressure within a predetermined pressure range in response to the gas request. To do.

  The circulation channel 23 is a channel through which gas and moisture discharged from the fuel cell 2 are circulated. An impurity channel 30 is connected to the circulation channel 23 via a gas-liquid separator 28 and an exhaust drain valve 29. The gas-liquid separator 28 collects moisture from the hydrogen off gas. The exhaust / drain valve 29 operates according to a command from the control unit 6, and discharges moisture collected by the gas-liquid separator 28 and hydrogen off-gas (fuel off-gas) including impurities in the circulation channel 23 to the outside. To do. The hydrogen off-gas discharged through the exhaust / drain valve 29 and the impurity channel 30 joins and dilutes with the oxidizing off-gas in the exhaust channel 12 in the diluter 5. The circulation channel 23 is provided with a circulation pump 31 that pressurizes the hydrogen off-gas in the circulation channel 23 and forcibly sends it to the hydrogen supply channel 22 side. The operation of the circulation pump 31 is controlled by the control unit 6.

  The control unit 6 detects an operation amount of an acceleration operation member (accelerator or the like) provided in the vehicle, and receives control information such as an acceleration request value (for example, a required power generation amount from a load device such as a traction motor). Control the operation of various devices in the system. In addition to the traction motor, the load device is an auxiliary device (for example, a motor of the air compressor 14 or a motor of the circulation pump 31) necessary for operating the fuel cell 2, and various devices involved in traveling of the vehicle. It is a collective term for power consumption devices including actuators used in (transmissions, wheel control units, steering devices, suspension devices, etc.), air conditioning devices (air conditioners) for passenger spaces, lighting, audio, and the like.

  The control unit 6 is configured by a computer system (not shown). Such a computer system includes a CPU, a ROM, a RAM, an HDD, an input / output interface, a display, and the like. When the CPU reads various control programs recorded in the ROM and executes desired calculations, various processes are performed. And do control.

  Specifically, the control unit 6 uses the temperature sensor 27 to detect the temperature in the hydrogen supply passage 22 on the downstream side of the injector 26 during operation of the fuel cell 2. When the temperature detected by the temperature sensor 27 is equal to or higher than the freezing point (zero degree Celsius under 1 atm), the control unit 6 controls various devices to generate the required amount of power with the fuel cell 2. Thus, the steady operation is performed by adjusting the oxidizing gas and the hydrogen gas. The adjustment of the oxidant gas is realized by controlling the rotation speed of the air compressor 14 in the oxidant gas system 3, adjusting the back pressure of the oxidant off-gas discharged from the fuel cell 2, or the like. The adjustment of the hydrogen gas is realized by controlling the shutoff valve 24 and the injector 26 in the fuel gas system 4, controlling the rotation speed of the circulation pump 31, controlling the exhaust drain valve 29, and the like.

  By the way, in the joining part A of the hydrogen circulation channel 22 and the circulation channel 23 of the fuel cell system 1, as shown in FIG. The moisture W that is forcibly sent to the merge portion A via 23 and the moisture W generated by condensation in the merge portion A remain. During the operation of the fuel cell system 1 in a low temperature environment, the water W remaining in the merging portion A moves to the upstream side (injector 26 side) of the hydrogen supply flow path 22 in the downstream portion of the injector 26. May freeze. In particular, the drive cycle of the injector 26 is increased for the purpose of suppressing the generation of irregular operating noise that is likely to occur when the operation with a small amount of required power generation from the load device is being performed (at the time of low load). In this case, there are many opportunities for gas discharge by the circulation pump 31 when the gas injection by the injector 26 is stopped. Thus, when the discharge of the circulation pump 31 is carried out when the injection of the injector 26 is stopped, the moisture W remaining in the junction A moves to the injector 26 side by the discharge pressure of the circulation pump 31, and the moved moisture W becomes hydrogen. The possibility of freezing in the supply flow path 22 is increased.

Therefore, the control unit 6, when the temperature detected by the temperature sensor 27 is below freezing point, as shown in FIG. 2, the injection timing of the hydrogen gas G _S into the merging portion A by the injector 26, the merging by the circulation pump 31 a discharge timing of the gas G _C to part a, to synchronize. Thereby, the back flow of the water | moisture content W which remained in the confluence | merging part A is suppressed, and obstruction | occlusion of the hydrogen supply flow path 22 resulting from the freezing of the water | moisture content in the downstream part of the injector 26 is suppressed. That is, the control unit 6 functions as control means in the present invention.

  Next, a control method of the fuel cell system 1 according to the present embodiment will be described using the flowchart of FIG.

First, the control unit 6 detects the temperature T in the hydrogen supply flow path 22 on the downstream side of the injector 26 during the operation of the fuel cell 2 (temperature detection step: S1), and the detected temperature. It is determined whether T is below the freezing point T ₀ (temperature determination step: S2). Then, the control unit 6 controls various devices to generate the required amount of power by the fuel cell 2 when it is determined in the temperature determination step S2 that the detected temperature T is equal to or higher than the freezing point T _0. Thus, the steady operation is continued by adjusting the oxidizing gas and the hydrogen gas (steady control step: S3). In the steady control step S3, the control unit 6 sets the drive cycle of the injector 26 at the time of low load (when the load is below a predetermined threshold) to the drive cycle at the time of normal load (when the load is equal to or greater than the predetermined threshold). Longer to suppress the generation of irregular operating noise.

On the other hand, when the controller 6 determines in the temperature determination step S2 that the detected temperature T is lower than the freezing point T ₀ , the injection timing of the hydrogen gas to the junction A by the injector 26 and the junction by the circulation pump 31 The gas discharge timing to the part A is synchronized (synchronous control step: S4). In the synchronous control step S4, the control unit 6 does not perform the noise suppression control (the drive cycle of the injector 26 at the time of low load is longer than the drive cycle at the time of normal load) as in the steady control step S3. Priority is given to suppressing the backflow of the water | moisture content W which remained in the part A. FIG. The control unit 6 repeatedly executes these process groups during the operation of the fuel cell 2.

  In the fuel cell system 1 according to the embodiment described above, the injection timing of the hydrogen gas to the junction A by the injector 26 and the gas discharge timing to the junction A by the circulation pump 31 in a low temperature environment. Since it can synchronize, it can suppress that the water | moisture content which exists in the confluence | merging part A flows backward upstream, and freezes in the injector 26 downstream part. Accordingly, the power supply state of the fuel cell 2 can be stabilized by suppressing the blockage of the hydrogen supply channel 22 in a low temperature environment.

  In the above embodiment, the temperature detected by the temperature sensor 27 provided in the hydrogen supply channel 22 (the temperature in the hydrogen supply channel 22 on the downstream side of the injector 26) is the freezing point (zero degrees Celsius under 1 atm). In the case where the temperature is lower, it is determined that the temperature is lower than the predetermined low temperature environment, and the synchronous control of the injector 26 and the circulation pump 31 is performed. However, the determination of the low temperature environment is not limited to this. For example, an outside air temperature sensor that detects the outside air temperature is employed, and when the outside air temperature detected by the outside air temperature sensor falls below a predetermined temperature, it is determined that the vehicle is in a predetermined low temperature environment, and the injector 26 and the circulation pump 31 are used. You may decide to implement synchronous control with.

  Moreover, in the above embodiment, although the example which mounted the fuel cell system which concerns on this invention in the fuel cell vehicle was shown, it concerns on this invention to various mobile bodies (a robot, a ship, an aircraft, etc.) other than a fuel cell vehicle. A fuel cell system can also be installed. Further, the fuel cell system according to the present invention may be applied to a stationary power generation system used as a power generation facility for a building (house, building, etc.).

1 is a configuration diagram of a fuel cell system according to an embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of a junction between a hydrogen supply channel and a circulation channel of the fuel cell system shown in FIG. 1. 2 is a flowchart for explaining a control method of the fuel cell system shown in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Fuel cell, 6 ... Control part (control means), 21 ... Hydrogen tank (fuel supply source), 22 ... Hydrogen supply flow path, 23 ... Circulation flow path, 26 ... Injector (open / close valve) 31 ... circulation pump, A ... confluence part.

Claims (8)

A fuel cell, a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, an on-off valve that adjusts the gas state on the upstream side of the supply channel and supplies it to the downstream side, A circulation flow path for guiding the gas discharged from the fuel cell to the supply flow path; and a circulation pump for forcibly sending the gas discharged from the fuel cell to the supply flow path. A fuel cell system in which a junction between a passage and the circulation channel is disposed downstream of the on-off valve,
When the temperature in the supply channel on the downstream side of the on-off valve is below the freezing point during operation in a low temperature environment of the fuel cell, fuel gas injection timing to the junction by the on-off valve, and the circulation pump Comprising a control means for performing synchronous control to synchronize the gas discharge timing to the merging portion with
Fuel cell system. The on-off valve is an injector;
The fuel cell system according to claim 1. The control means performs steady control for controlling the injector to drive at a predetermined drive cycle when the required power generation amount from a predetermined load device is equal to or greater than a predetermined threshold value, while the required power generation amount falls below a predetermined threshold value Sometimes, noise suppression control is performed to control the injector with a driving cycle longer than the driving cycle.
The fuel cell system according to claim 2. When the temperature in the supply flow path on the downstream side of the injector is below the freezing point during operation of the fuel cell in a low temperature environment, the control means is a case where the required power generation amount is below a predetermined threshold value. Also performs the synchronous control without implementing the noise suppression control,
The fuel cell system according to claim 3. A fuel cell, a supply channel for flowing fuel gas supplied from a fuel supply source to the fuel cell, an on-off valve that adjusts the gas state on the upstream side of the supply channel and supplies it to the downstream side, A circulation flow path for guiding the gas discharged from the fuel cell to the supply flow path; and a circulation pump for forcibly sending the gas discharged from the fuel cell to the supply flow path. A method for controlling a fuel cell system, wherein a joining portion between a path and the circulation channel is disposed downstream of the on-off valve,
When the temperature in the supply channel on the downstream side of the on-off valve is below the freezing point during operation in a low temperature environment of the fuel cell, fuel gas injection timing to the junction by the on-off valve, and the circulation pump And a synchronous control step of synchronizing the gas discharge timing to the junction with
Control method of fuel cell system. The on-off valve is an injector;
The control method of the fuel cell system according to claim 5. A steady control step of driving and controlling the injector at a predetermined drive cycle when a required power generation amount from a predetermined load device is equal to or greater than a predetermined threshold;
A noise suppression control step of controlling driving of the injector at a driving cycle longer than the driving cycle when the required power generation amount falls below a predetermined threshold,
The control method of the fuel cell system according to claim 6. When the temperature in the supply flow path on the downstream side of the injector is below the freezing point during operation in a low temperature environment of the fuel cell, the noise suppression control is performed even when the required power generation amount is below a predetermined threshold value. Performing the synchronous control step without performing the step;
The method for controlling a fuel cell system according to claim 7.

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